The conventional shredders for cutting paper use a plurality of cutting blades and spacers engaging over a rotary cutter shaft, and the shearing force that two parallel and opposite rotary cutter shafts produce for transferring and cutting the paper-to-be-cut along a longitudinal direction into strips. Shredders can be classed into two types, the stripe-cut shredders and crosscut shredders, according to the machine cutting style. The former shredders arrange cutting blades to the rotating cutter shafts in a manner to cutting the paper in a longitudinal direction to form strips. The later shredders include blades that include more than one cutting edge, and each cutter is disposed helically along the rotary cutter shaft for first cutting paper along a longitudinal direction into strips and then cutting paper along a horizontal direction into approximate 4 mm×40 mm paper chips.
By referring to the assembled perspective view of a conventional blade illustrated in FIG. 1 and a planar view showing the operation of the conventional blade in FIG. 2, the conventional blade is made by punching a sheet metal having a thickness of approximately 2 mm into a circular blade by a mold. The blade includes a polygonal central hole A1 through which a rotary shaft may pass. The blade also includes cutting edges A2 that are spaced in 120 degrees apart around the periphery. As shown, when two blades are arranged on the rotary shafts B in a back-to-back manner to combine into a set of blades A, the cutting edges of the two blades assume a V-like edge A3. The opposite rotary shafts B′ space the two blades apart by spacer (not shown) in a face-to-face manner to form a set of blade A′. When the paper-to-be-cut passes through the two reverse rotary shafts B, B′, the opposing rotation of the periphery of the blades, that is, flanks A4 and flanks A4, will cut the paper like scissors. The opposing rotation of cutting edges A2 and the opposite flanks A4 will then cut the paper along a horizontal direction into 4 mm×40 mm paper chips.
During operating of the conventional blades, to ensure smooth cutting of the paper along the horizontal direction, sharp blades with proper orientations are needed. However, because the blades are formed by a punch molding, the mold wear that increases with the time will reduce sharpness of the blade edges, which does not improve until replacing the mold, to result in inconsistent quality. To ensure quality of the blades, it is necessary to shorten the service term of the mold, which results in increment of the cost. In addition, in the conventional blades, the thickness of the blade is the same as the width of the paper-to-be-cut. To ensure the strength of blades while cutting along the horizontal direction, the blades cannot be too thin, or else the blades tend to deform or fracture. Such a limitation attributes to the high material cost, which is less competitive as compared to the current market price. In addition, because the thickness of the conventional blades is same as the width of the paper-to-be-cut, and because the location of the width define the horizontal cutting points, the narrower width of cross-section is, the smaller output power is needed to cut along the horizontal direction. In other words, the motor can supply a minimum power for cutting along the horizontal direction, that is, to reduce the power consumed by the motor. But because of the width of the paper-to-be-cut by the conventional blades is 4 mm, the motor needs to output higher power to drive the blades and flanks moving in opposing directions to cut the paper along the horizontal direction smoothly.